Cyanohydrins are traditionally prepared by the addition of HCN to the corresponding carbonyl. The reaction is typically catalyzed by base or an enzyme. Because of the hazards with HCN, other less dangerous cyanation reagents are often used. •
Trimethylsilyl cyanide, affording the silyl ether derivative of the cyanohydrin •
Diethylaluminium cyanide, especially for less reactive carbonyls •
Diethyl phosphorocyanidate (DEPC) and lithium cyanide •
Acyl cyanides (RC(O)CN)
Transhydrocyanation Acetone cyanohydrin, (CH3)2C(OH)CN is the cyanohydrin of
acetone. It is generated as an intermediate in the industrial production of
methyl methacrylate. In the laboratory, this liquid serves as a source of HCN. The process is called
transhydrocyanation, where acetone cyanohydrin, is used as a source of HCN. Thus, acetone cyanohydrin can be used for the preparation of other cyanohydrins, for the transformation of HCN to
Michael acceptors, and for the
formylation of
arenes. Treatment of this cyanohydrin with
lithium hydride affords
anhydrous lithium cyanide: :
Asymmetric cyanohydrin formation Formation of cyanohydrins introduces a chiral center for aldehydes and for unsymmetrical ketones. The enantioselective hydrocyanation has attracted some attention for the preparation of 2-chloromandelic acid, a drug precursor. File:Acetone cyanohydrin.svg|
Acetone cyanohydrin File:Mandelonitrile-2D-skeletal.svg|
Mandelonitrile, occurs in small amounts in the pits of some fruits. File:Amygdalin structure.svg|
Amygdalin, a naturally occurring cyanogenic glycoside ==See also==